Remeber how you learned that a pure liquid distills within a narrow boiling point range, but that narrow boiling point doesnt necessarily imple a pure liquid? Keeping that lesson in mind, explain this: you know without a doubt from spectroscopic technique that your product mixture contains 2 distinct products... yet your TLC plate shows only one spot. How is this possible? The, your research advisor tells you thats its really not that unusual to encounter this kind of conflicting data and that it is often easily resolved with a little more bench work. What should you do to clear up the issue using the TLC?

Consider the following question and answer.

Give an example of a homogeneous mixture: "WATER, because it is made up of two different elements - hydrogen and oxygen, and the comeposition is even throughout."

Which aspect of the students answer are correct? Which are incorrect?

7) How many grams of boric acid should be used in compounding the following prescription: (4 points) Rx Lidocaine HCl 1% (E=0.20) Pilocarpine HCl 0.5 % (E= 0.24) Boric acid qs (E=0.52) Purified water ad 60 mL Make isotonic solution Sig: 1 drop in each eye

Calculate the enthalpy of the reaction 4B(s)+3O2(g)→2B2O3(s) given the following pertinent information: B2O3(s)+3H2O(g)→3O2(g)+B2H6(g), ΔH∘A=+2035 kJ 2B(s)+3H2(g)→B2H6(g), ΔH∘B=+36 kJ H2(g)+12O2(g)→H2O(l), ΔH∘C=−285 kJ H2O(l)→H2O(g), ΔH∘D=+44 kJ

A 100.0 mL sample of 0.20 M HF is titrated with 0.10 M KOH. Determine the pH of the solution after the addition of 200.0 mL of KOH. The Ka of HF is 3.5 × 10-4.

Answer: 8.14 but how do I get this?? I'm so lost!

Consider the following reaction. It is occuring in a closed system and it is currently at equilibrium:

Label each of the following statements with is effect on the reaction
shift towards products or shift towards reactants or no change: Removing oxygen gas.
shift towards products or shift towards reactants or no change:  Cooling the reaction vessel.
shift towards products or shift towards reactants or no change:  Removing water vapor from the vessel.
  shift towards products or shift towards reactants or no change:  Increase the size of the vessel.
  shift towards products or shift towards reactants or no change:  Decrease the pressure on the reaction vessel

The ethyl mercaptan, C2H5SH, concentration in a mixture was determined by shaking a 1.534-g sample with 60.0 mL of 0.01293 M I2 in a tightly stoppered flask:

2C₂H₅SH + I₂ → 2C₂H₅SSC₂H₅ + 2I^- + 2H⁺

The excess I2 was back-titrated with 10.72 mL of 0.01425 M Na₂S₂O₃:

2S₂O₃^2- + I₂ → S₄O₆^2- + 2I^-

Calculate the percentage of C₂H₅SH (FM = 62.13 g/mol) in the mixture.

(a) 5.67% (b) 3.32% (c) 1.24% (d) 4.33%

(please show work)

An air-purification method for enclosed spaces involves the use of "scrubbers" containing aqueous lithium hydroxide, which reacts with carbon dioxide to produce lithium carbonate and water: 2LiOH(aq) + CO2(g) → Li2CO3(s) + H2O(l) Consider the air supply in a submarine with a total volume of 1.6 × 105 L. The pressure is 0.9970 atm, and the temperature is 25°C. By how much would the pressure in the submarine drop if 2.35 kg of LiOH were completely consumed by reaction with CO2?

atm

A 0.120-L sample of an unknown HNO3 solution required 29.1 mL of 0.200 M Ba(OH)2 for complete neutralization. What was the concentration of the HNO3 solution?

Calculate the ph after mixing 100 ml of .075 M ammonium chloride with 76 ml of .1 M LiOH

Using the particle in the 1-D box model, estimate the first 4 energy levels of the π-network in hexatriene, C6H8 (H2C=CH–CH=CH–CH=CH2). To calculate the box length, assume that the molecule is linear and use the values 135 and 154 pm for the C=C and C–C bonds, respectively. Only 2 out of the 6 ‘π-electrons’ of the 6 C-atoms can occupy each energy level (Pauli exclusion principle). Ignore the rest of the electrons (forming the core and the ??-bonding network). Sketch and label an energy level diagram showing the occupied levels and the first unoccupied one. What is the wavelength of the photon required to induce the HOMO-LUMO transition? Derive the expression for the photon’s wavelength symbolically! How does your numeric result compare with the experimental value of 240 nm?

How many moles of sodium hydroxide would have to be added to 250 mL of a 0.436 M acetic acid solution, in order to prepare a buffer with a pH of 4.630?

moles

Coke can be converted into CO in following reaction CO2(g) + C(s) -> 2CO(g). A coke that contains 84% carbon by mass and the balance noncombustible ash is fed to a reactor with a stoichiometric amount of CO2. The coke is fed at 77 oF, and the CO2 enters at 400 oF. Heat is transferred to the reactor in the amount of 5200 btu/lbm coke fed. The gaseous products and the solid reactor effluent (the ash and unburned carbon) leave the reactor at 1830 oF. The heat capacity of the solid is 0.24 btu/(lbm.oF) Calculate the percentage conversion of the carbon in the coke. (Provide your answer in decimal format, NOT percentage format!)

How many milliliters of 1.27 M KOH should be added to 100. mL of solution containing 10.0 g of histidine hydrochloride (His·HCl, FM 191.62) to get a pH of 9.30?

In an experiment where you standardize EDTA with calcium carbonate and then have EDTA as the titrant and zinc as the analyte to determine the amount of zinc, which of the following are potential sources of error in the determination of the mean and relative standard deviation for the amount of zinc in your unknown?

Select all answers that apply.

1) Lack of homogeneity in the indicator solution

2) Not dissolving calcium carbonate completely

3) Inconsistencies in pipetting the zinc unknown

4) Systematic error in the buret calibrations

5) Failing to quantitatively transfer calcium carbonate

6) Sharing the indicator bottle

7) Over-titrating